A good way to get involved in the OpenStreetMap project is to upload GNSS (GPS, Galileo, GLONASS, BeiDou/COMPASS, etc.) traces. Recorded by your satellite receiver or mobile phone, the typical trace is a record of your location every second, or every meter (“tracelog”). Convert it to GPX format if it wasn't done for you automatically. The collected data can be displayed as a background of thin lines or little dots within the map editor. These lines and dots can then be used to help you add map features (such as roads and footpaths), similar to tracing from aerial imagery.

For a variety of reasons, you may want to edit a GPS track log before uploading it to OSM. If you followed the conversion step before now, the track log should be in GPX file format.

Warning:

You should only upload raw data you collected yourself in the real world.

OSM is interested in the raw data, so you shouldn't edit your tracks to match what you would like to see mapped. In particular, don't edit the locations of trackpoints, just remove bad ones and split the tracks as required.

Reasons

To protect your privacy:

Your GPS tracks can reveal your exact address and show when you were where. This can give people a lot of information you don't want them to have. You may want to exclude the area around your house (Using filters with GPSBabel shows how to do that with gpsbabel) and possibly modify the timestamps.

To improve the remove or correct bad data:

You may want to remove points where your GPS receiver had poor reception (say you were inside a building).

Also, if you spent a while at some place, the resulting cloud of points is not that useful for mapping.

If the receiver produced implausible results:

distance between trackpoints more than 500 m,

speeds higher than 300 km/h lower than 1 km/h (values can be computed by gpsbabel)

Organization:

You may want to split your logs into parts depending on some criteria. For instance, separate the flight log and the bus trip from the airport. This allows more accurate tagging of the uploaded logs.

To reduce the data volume, you may want to :

compress a track to reduce the number of points and speed up uploading.

to delete sections of data which have already been uploaded or are not relevant.

Options

GpsMaster is a free and open source desktop application used to create, view, edit and analyse GPX files

GPSBabel provides filters (see using filters with GPSBabel). Some of these only work on waypoints, so you may have to convert a track to waypoints and back (gpsbabel allows this).

JOSM permits reading and writing GPX files. By converting the GPX layer to a data layer, it can be edited, then saved again as a GPX file, or directly uploaded to OSM using EditGpx plugin. Elevation and metadata is preserved since JOSM version 14163.